我的 UserControl 中的 DependencyProperty Set 和 Callback 没有发生

Question

我正在尝试在 WPF 中创建一个简单的 UserControl，以便在我的其他应用程序中重复使用。这是一个简单的 DateRangePicker。某些控件的属性绑定到子 UI 元素，因此我实现了 INotifyPropertyChanged。我的 control.xaml.cs 如下所示（仅相关部分）

public partial class DateRangePicker : UserControl, INotifyPropertyChanged
   {
      public DateRangePicker()
      {
         InitializeComponent();

         DataContext = this;
      }

      public event PropertyChangedEventHandler PropertyChanged;

      protected void RaisePropertyChangedEvent(string propertyName)
      {
         if (PropertyChanged != null)
         {
            var e = new PropertyChangedEventArgs(propertyName);
            PropertyChanged(this, e);
         }
      }


      public static readonly DependencyProperty InitialFromDateProperty =
         DependencyProperty.Register("InitialFromDate", typeof(DateTime), typeof(DateRangePicker), new PropertyMetadata(default(DateTime),
      new PropertyChangedCallback(OnInitialDateRangeChanged)));

      public static readonly DependencyProperty InitialToDateProperty =
         DependencyProperty.Register("InitialToDate", typeof(DateTime), typeof(DateRangePicker), new PropertyMetadata(default(DateTime),
      new PropertyChangedCallback(OnInitialDateRangeChanged)));

      public static readonly DependencyProperty SelectedFromDateProperty =
         DependencyProperty.Register("SelectedFromDate", typeof(DateTime), typeof(DateRangePicker), new PropertyMetadata(default(DateTime), null));

      public static readonly DependencyProperty SelectedToDateProperty =
         DependencyProperty.Register("SelectedToDate", typeof(DateTime), typeof(DateRangePicker), new PropertyMetadata(default(DateTime), null));


      public DateTime InitialFromDate
      {
         get { return (DateTime)GetValue(InitialFromDateProperty); }
         set
         {
            SetValue(InitialFromDateProperty, value);
         }
      }

      public DateTime InitialToDate
      {
         get { return (DateTime)GetValue(InitialToDateProperty); }
         set
         {
            SetValue(InitialToDateProperty, value);
         }
      }

      public DateTime SelectedFromDate
      {
         get { return (DateTime)GetValue(SelectedFromDateProperty); }
         set
         {
            SetValue(SelectedFromDateProperty, value);
         }
      }

      public DateTime SelectedToDate
      {
         get { return (DateTime)GetValue(SelectedToDateProperty); }
         set
         {
            SetValue(SelectedToDateProperty, value);
         }
      }

      private static void OnInitialDateRangeChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
      {
         DateRangePicker control = (DateRangePicker)d;
         control.RefreshLists();
      }

我的测试应用程序 xaml 托管控件的文件如下所示（包括命名空间的一些行已被删除）：


<Window x:Class="WpfApp3.MainWindow"
        xmlns:ControlDateRangePicker ="clr-namespace:SurfServer.Apps.Common.UI"
        xmlns:local="clr-namespace:WpfApp3"
        Title="MainWindow" Height="414.831" Width="565.808">
    <Grid>
        <ControlDateRangePicker:DateRangePicker
                        InitialFromDate="{Binding InitialFromDateVM, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}" 
                        InitialToDate="{Binding InitialToDateVM, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"
                        SelectedFromDate ="{Binding SelectedFromDateVM, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"
                        SelectedToDate ="{Binding SelectedToDateVM, UpdateSourceTrigger=PropertyChanged, Mode=TwoWay}"
                        HorizontalAlignment="Left" Margin="136,78,0,0" VerticalAlignment="Top" Width="347"/>
    </Grid>
</Window>

我的测试应用程序 xaml.cs 看起来像这样


public partial class MainWindow : Window
   {
      public MainWindow()
      {
         InitializeComponent();
         try
         {
            var viewModel = new SampleViewModel();
            DataContext = viewModel;
            viewModel.Initialize();
         }
         catch (Exception)
         {
            Close();
         }
      }
   }

我的测试应用程序的 ViewModel 如下所示：

class SampleViewModel : ViewModelBase
   {

      private DateTime m_dtInitialFrom;
      public DateTime InitialFromDateVM
      {
         get => m_dtInitialFrom;
         set
         {
            m_dtInitialFrom = value;
            RaisePropertyChangedEvent(nameof(InitialFromDateVM));
         }
      }

      private DateTime m_dtInitialTo;
      public DateTime InitialToDateVM
      {
         get => m_dtInitialTo;
         set
         {
            m_dtInitialTo = value;
            RaisePropertyChangedEvent(nameof(InitialToDateVM));
         }
      }

      public DateTime SelectedFromDateVM
      {
         get;
         set;
      }

      public DateTime SelectedToDateVM
      {
         get;
         set;
      }

      public void Initialize()
      {
         InitialFromDateVM = new DateTime(DateTime.Now.Year - 1, DateTime.Now.Month, DateTime.Now.Day);
         InitialToDateVM = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day);
      }

如您所见，测试应用程序的视图模型中的一些属性绑定到我的控件的 (DateRangePicker) 依赖属性。现在我面临的问题是，虽然我试图在我的测试应用程序的 ViewModel 中设置初始值（在 Initialize 方法中），但看起来绑定不起作用并且我没有在我的控件中获得回调（实际上，我什至无法击中依赖项属性本身的 'set'）。我想在这里做错什么？

Answer 1

您必须从 DateRangePicker 构造函数中删除设置 DataContext。因此，您的 UserControl 的 DataContext 不是您的 ViewModel SampleViewModel，而是 UserControl 本身。

public partial class DateRangePicker : UserControl, INotifyPropertyChanged
{
      public DateRangePicker()
      {
         InitializeComponent();

         //DataContext = this; REMOVE
      }
}

我的 UserControl 中的 DependencyProperty Set 和 Callback 没有发生

DependencyProperty Set and Callback in my UserControl not happening

c#

wpf

user-interface

user-controls

mvvm